Certain construction sites are subject to storm water or tidal flow penetrating the soil. Conventional slab-on-grade or pile-slab structural systems do not allow water to penetrate them. A rising tide will create an upward pressure on the lower surface of the slab. A downward pressure will be exerted by storm water that lies above the slab and cannot drain. The Department of Environmental Conservation in certain flood zone areas requires that any such water be allowed to penetrate the site, including any structure, to maintain and replenish the water table.
Systems that allow water to penetrate a foundation are known and, heretofore, have been configured in different ways. Some examples of foundation drains in the prior art are seen in the following U.S. patents:
Phillips, U.S. Pat. No. 5,784,838; Parker, U.S. Pat. No. 5,771,643; Jackman, U.S. Pat. No. 5,630,299; and Beechen, U.S. Pat. No. 4,245,443; all show a drain unit that extends around the periphery of a basement wall for draining water to beneath the floor.
McPherson, U.S. Pat. No. 5,775,039, depicts a drain that collects water entering between the wall and footing, and conveys the water to a sump under the floor.
Owens, U.S. Pat. No. 5,156,494, illustrates an active system for pumping water to points around the periphery of a foundation to equalize stress upon the foundation.
Compernass, U.S. Pat. No. 3,847,630; and Shaw, U.S. Pat. No. 4,453,844; both disclose porous concrete which is water permeable.
While the above-described systems serve a drainage function, they display serious shortcomings with respect to satisfying the Department of Environmental Conservation requirements. Furthermore, such conventional systems do not relieve the upward and downward water pressure which minimizes stress on the slab. The above-described systems relieve water pressure only on a unidirectional basis, not across the slab. In order to relieve both upward and downward pressure on the slab, while maintaining structural integrity, several conditions must be met. Firstly, water must freely penetrate the slab in both directions: from the upper surface through the slab and out the lower surface, and also in the reverse direction, from the lower surface through the slab and out the upper surface. Secondly, the water must penetrate evenly over the surface of the slab, not just around the perimeter, to relieve pressure over the entire surface area. Thirdly, the slab must not be compromised in strength throughout it's service life. The inventions of Phillips, Parker, Jackman, and Beechen drain water from the upper surface to the lower surface around the perimeter only, not evenly over the surface. McPherson conveys water not from the upper surface, but from only the footing perimeter to the lower surface, and again not evenly over the surface. Owens does not allow water to flow freely in both directions. Owens pumps water to lower surface points only, around the periphery only, and upon demand from stress sensors, not upon demand from the environment. The porous concrete of Compernass and Shaw allow water, including salt water, full access to the reinforcing bars in the concrete. Within a short time, the carbon steel bars will be corroded to a useless condition, weakening the slab and leading to structural failure. Furthermore, the special porous concrete mix is expensive, and may not meet the structural strength requirements of the job.
Accordingly, there is a need to provide a breathing system for concrete slabs that will allow water to penetrate the slab from both directions, upward and downward.
There is a further need to provide a system of the type described and that will allow water to penetrate evenly over the entire surface of the slab.
There is a still further need to provide a system of the type described and that will not compromise the strength of the slab throughout it's service life.
There is a yet further need to provide a system of the type described and that is cost-effective and easy to install.